Frequency-regulating system



Nov 25,` 1930. H. cHlRElx 1,732,807

FREQUECY REGULATING SYSTEM Filed Sept. f3. 1925 2. Sheets-Sheet 2 INVENTOR ATTORNEY fiuence ybytheaid of aFaraday cage,`

i 30 which is rectied by `a secondfdetector.

VPatented Nov. 25, Q

i i i 1,782,807'

c nnnmciiiiiiiix, oriifanis, rnNcEjffj; y; f y j "lFnnQUENcrQRnGULATING1SYSTEM,

Appiibatiiilia september s,1925,seiiai `N01 155,086, aha-in France september io, 19.24.`

The present invention has asits object to provide means: adapted to insure Aperfect,`

regulation of .the requencymf thecurrents generated by "vacuum tubes, byaics, or ina 1 "5 more general way by all autoeregenerator systeinsrin 1wl`iich theirequency produced depends`,:'inthe jlast analysis, upon the electric constants l:orf characteristics of the cirie Another objectV of .the invention is to; furnishfin such. a `system particularly simple keying method." "Ti lTlieprinciple underlying the invention maybe set forth as follows The waves' sent out by the generatoritobegregulatedvare heti erodyned.` with a small auxiliary generator` or'heterodyne whose requencyfmay be re#` garded as `perfectly stable. This auxiliary `-orstandard generator maybe constitutedby p ahvacuumtubefof small size` fed vfrom batteries, a` piezo-electrid crystal, orf any @other source of constant high @frequency currents,

. connectedwith anoscillatory circuit',A the as'- seinbly rbeing `safeguarded ,from youtside in- By meansloi` aiirst detector, beatsotrelatively low,l frequency are; produced.` "`iThese .beats set" up in a circuit, Lwliich` is `tuned or `practically tuned, ,an` alternating `voltage The ensuing direct curreiitis thereuponcused in 1 such awayfas tocause the `frequency lof; the

`main generatorto dierfrom tliatotthe auX- iliary one byf-a constant value.,V Itthen the fl `frequency of the la'tterisv constant so 1also :willbethe requencyofthe former. gi

l One method of using this `re t'iied current consists incausing it to saturate` to a greater or lessdegree the irfonco-re `of a self-induc- 40 i tion coilins'erted i-n `the circuit of theprincipal generator." Another method consists iii using therectiled current to'vary the characteristics of a vacuum tube connected inA an "appropriate, manner` to ,the :circuit` of "the i principal generatortofvarythe frequency of 1 ythedlatter` inthe `correct gseiisef 'It can bev readily seeiifthatrregardless of thefparticular method* usedfla closed .i cycle is 'obtained "through whichlthe Vfrequency of: oscillations constant value1? vfromV the i fredueificy` of (the i standard generator.`

"The frequency Tot` thefcurrents by the auxiliary, or standard transmittermay moreover: 4be changed :by the useI cfa` key. or manipulator acting upon` the lsaid `standard transmitter,` to modify ina likewisef constant manner the frequency of the main-,transmit- The invention maybe l best understood i accompanying drawing in which p AFig. lsliows ,one modification conforming to the invention l guFig. y 2 fshows a.. detailed modification of i certaingcircuits in-Figl and Fig. '3 shows a further modification of the invention.`

Vfrom thev following `detailedvdescription .whichgshould be readin connection.with` the i Referring .to Fig, itil@ pfineipaif gener! j,

= ator,l isgrepresentedi at4`20 and `has ii'i. .its out- 2, together with` thehi'gh frequencyfwindings; V3 Y of saturated A#self-inductioni coil,` of

through, which passes` a rectifiedv direct cur vrent as hereinafteri, explained.` 1j VThese windings are so connected tliatthe iiiducedhigh frgapueiicy` voltages subtract.` yThe arrangegenerator or i localiheterodyne is shown at E 5 which represents theupriiiiary windings i mentf'for such` a saturated self-inductioncoil scribedggA constant* frequency auxiliary 'which `maygconsistfoi a` vacuumftube oscillatorg a piece of quartz,possessinglpiezoelec# tlpropertes `and vibrating at mechanical frequencymmiy Otherrfcrm Of Gelman# flie- `auxiliarygenerator. @are inserted `the "selffin- Y replaced `by a condenserjif desired..4 `This generator iscouiled through the coil Tio, an' i v :oscillatory circuit `9` .preferably i, to the y ,mean frequencygiotthe main.;1 transmitter .u

"V50 of the priiicipalgenerator `will "diier lby a andthe auxiliarytraiisnilitterhQifliQQQFOQYIlQ! on f This voscillatory circuit receives energy from the kgenerator and the generator 20, causing a beat frequency therein. The beat frequency is first detected by a vacuum tube 11 having a shunted condenser in its grid circuit and is then transferred by the coil 12 to the oscillatory circuit 13. This beat frequency is preferably chosen inside the range of audibility, say of an order of 5000 cycles per second. If the oscillatory circuit 13 is tuned to a higher frequency, say 6000 cycles, and conveniently damped an alter nating` potential will be set up across the common terminals of the condenser and self induction coil which is again detected by the tube 15 having in its grid circuit a shuiited condenser 14. The plate circuit of the tube 15 contains the windings V4 which will therefore have rectified current flowing through them, whose value will be determined by the y closeness of the heat frequency to the natural frequency of the circuit 13, that is if the beat frequency approaches the frequency of this circuit the current will increase and'if the beat frequency recedes from the frequency of this circuit the current vwill decrease. The coils 4 are shunted by condenser V16 which has the effect of attenuating the fluctuations of the rectified current and prevent-ing at the same time all reactive effects of the circuit 1-2 3 on the tube 15.

A numerical example may be cited tofbetter gi'asp the operation. Suppose that currents or waves of a frequency of 3,000,000 cycles are to be transmitted. Then the auxiliary generator 5-will have to be regulated so as to produce a frequency of 3,005,000 cycles giving the 'main self-induction coil 1 a value such that under these conditions there is effectively obtained a frequency of 3,000,000 cycles. If the damping of the circuit 13 is conveniently chosen, this working condition will correspond to aY mean direct current in the windings 4 (with va certain margin either way).

It will furthermore be seen that, if for some reason or another, the frequency of the main generator has a tendency to increase, the beat frequency will have a tendency to decrease, consequently also the current in the oifrcuit 13, and the direct current. in the plate circuit of the detector 15. And as the direct current tends to decrease, the saturation also shows a tendency to fall off, and as a. consequence the inductance ofthe saturated self-induction coils tend to increase in value which prevents the main osc-illator from growing in frequency. The developments arev just the contrary of what has been stated whenever there is a tendency for a drop in frequency. In view of the fact that mechanical inertia is wholly absent, and that the' time-constants of the various circuits can be made verylow, the regulation takes place instantaneously.

Fig. 2 illustrates a somewhat improved are rangement. 12 corresponds to 12 in Fig. 1 and acts as a primary of the transformer whose secondary 13 works upon a tuned shunt 14 15.. The space between grid and filament in detector 17 is taken to the terminals of the 4entire tuned shunt, whereas the space between the plate and the filament is brought to the terminals of the self-induction coil 14 or the capacity 15 (as shown in the figure). The windings 4 of the saturated self-induction coil correspond to the windings 4 of Fig. 1. It will be readily seen that the operation is the same, but if in this case thecurve of the detected direct current as a function of the frequency applied at 12" is plotted, it will be found that this graph is a straight `line about the natural `frequency `of the tuned shunt, whereas in the case of Fig. 1 there is found a curve with a downward concavity. This circumstance is evidently due to the fact that below the Vresonance frequency, the grid and the plate potentials are co-phasal, and that beyond the said point they are, on the contrary, in Aphase opposition. Nothing of .that Akind is present in the case of Fig. 1 where the plate potential is furnished by the cell 18. This offers a certain advantage; as `a matter of fact, the auxiliary transmitter can be so regulated that the beat frequency is made equal to the natural frequency of the oscillat-ing shunt whereas in the.:case of the arrangement in Fig. 1 it is necessary to keep on one side thereof, whereby greater sensibility is realized, Vwhile yet preserving a stable working condition.

The saturated self-induction coils shown in this arrangement ai'e of extremely small volume or size. Bearing in mind that `a tube transmitter outfit, even if no special precautionary means land measures are adopted, insures a stabili-ty in frequency of 1/1000, it will be clear that the variation of the selfinductance attains 1/1000 of the self-inductance 1 hence, the variation in reactive power stored up in this selffinduction coil should not be more than 1/1000 the vtotal reactive power.-

Before proceeding to the description of the t modification in Fig. "3 vit should be fixed in mind that the invention as thus far described comprises two essential parts, the first feature relating to the production of a current with `an amplitude varying very rapidly with the frequency, while Vthe second characteristic covers the utilization of this current in a saturated self-inductance coil.

i The embodiment shown in Fig. 3 discloses .improvements upon both .of the main chaiacif.

teristics of the invention. More particularly speaking, the beat currentobtained after the first detection is amplified by an amplifier arrangement of any desired type and comprising a` pluralityqof stages` if desired.

" The second elieii" of'ja'i-'siinple resonant* or tune circuit' (as y shown ein Figi 1) 1 a filter comp-rising" several fstafges 1s used-,` this ar.-

. rangement `presentin'g the advantage of "inv creasing "the: selective lp'roperties ofthe "circuit infar greaterproportion-than thetime constant. w detection is furthermore "ef- `fe`cted` in a particu] ajr manner if by "having ree courseto thefbeat currents forwholly or par `tially supplying the energy requiredfforthe `heating ofayalve, insuch 'manner that Wheifl lthe `amplitude lof thei beat current's in- ""cr`eases, the therniionic' "emission of thevalve in"VA question lgrows Very Y rapidly. i In `virtue suchfeXt-reinely rapid groyvthin"thermioiiic r emission as function" off the` tempe`ratu1`f"` 'there resultslan"equlvalent'inc'rease in tuning Q and resonance!A frequency of theyprincipal generatorto obtain a beatI frequency; which passes througha detector 22. The output of the detector 22 is amplified by the multi-stage amplifier 23 and impressed on a filter 24 which is analogous in its operation to the circuit 13 in Fig.` 1.

The output of this filtering circuit is ampli# fied by the tube 25 and impressed on a trans- `former 26 Whose secondary serves to ener gize the filament of the two-electrode Valve `27, A battery' 28 may be usedin series with this secondary to assist in the energizing -`actioni'f, desired. The electron-emission of i. Valve27 is thereby controlled by-the cur` rent in the secondary of thejt'ransformer 26 and the Value of this: current depends on the beat frequency formed by heterodyning the output of generator 33 with the constant hetero-dyne 21. The Valve or detector 27 Will serve to transfer the alternating current of variable y amplitude into a directcurrentV which isvalso of variable amplitude. This directcurrent is impressed across the resist- 1 ance 30 in parallel with `the filament grid circuit of a vacuum tube 31, abattery 29 being provided inl the output circuit of de- 'tector 27 to' overcome the drop' in Vthe tubeA andfthe drop in the resistance 10. The tube 31`acts as a lvariablel resistance and has its understood. cipal generator undergoes a slight change the current supplied at the of the filter 24 `Varies in amplitude, the temperature: of the plate` filament circuit connected across the` condenser 32 in the grid circuit ofthe generator" 3 3. `This plate circuit also includes choke coils 35., The principal generator 33 may be energizedin any desired manner, a

i coilB representing the energizing means in r the present case.

The operation of this system will be readily If the frequency of Athe prin- ,filament bof." 'valve i271 ehangesilandf sin' 'consel quence Ltheelectron-emission of the :valve undergoes consider'able ivaria'tons Theser rarifations causeV a great modificatonfim the i potential applied gat the fgridwofI 'tuber 31' .and therefore correspond-ing modifications in the resista-nce ofthepla'te-filament of this tube.

A-rIheselast modifications `in turn :resultlin l a yariationin the Umain potential inthegrid ofoscilllatorl i 3?` causing Variations in 1 the l frequency produced, -such 1 variations fbeing `of such` a :sense thattlieytend to correctthe OriginalsVfllillQIlS` which have-given rise to While'- i `have indossa the invention Ain seyeral specific modifications `it Will be fobyious. that r many modifications will readily ple, the' heterodyne generator may be caused to interfere with the harmonics or overtones l o 1v `ifithe1 Wave sentout bytheA rincipal genera# tor `instead of causing it to interfere directly with thefundamentalwave. 1.1

occurfto `thosetslzilledin thearty for exainp Aci v The rectie'dcurrent o'flyariable zimplitude linaylilewise be used for other purposes than the one ofsaturatinglaniron icore choke coil i or of'varyingthe electron emissiontofrthe V Valve rectified.` It Vcouldbe used asWellto cuit .or in `thecheatingcircuit `ofQthe three electrodejgeneratoritube. I intend"` `to `be limited therefore; only` :as indicated by `the "scope of theQfolloWingiclaims. i f

,7:5 1;. A"constant?frequencygenerating system,y

*excite a dynamowhose;potentialicould be appliedin the plate circuitpinthe gridcirr i y comprising fan` oscillation L generatori and `a constant .frequency .1 heterodyne arranged to fbeattherewith1` forl producingaa beat s Afrequency, anioscillatory circuittuned td said beat frequency,.rectifyingineansiassociated Y `with said. beatcfrequency circuit, `and "frep `quency fcoinpensatingfmeans included inl the genera-tor output 'circuit controlledilby the rectifedbeatlfrequencycurrents forlafecting u a' constant relationship@ between the heteroy -dynef` constant frequency and `the geraneratoik1 y i 2. A i systemfor i "frequency i Acurrents ofa desiredconstant frequencygcom- `pr1sing an oscillation -generator;` alocal heterodyne forbeating with thegenerated y frequency,` "a: circuit .tunedtosaid beat `fre- .y fquencyyfrectifying.means `for `producingfa` y direct current" proportional to" thel beat fre! 'i quencyyV saidl beat frequency Varying with yariations in "the generated W frequency, and

nieanscontrolled by a change in'zrectifiedbeat frequency current for` affecting` a change fin l thveielectrical.characteristicsoffthe frequency i v`controllingicircuit ofQtheggenerator forme-.

servelthedesiredfrequency.e i. i

lilnia frequency control systeinganoscilp lation generatorandi` a local#ffheterodyne` ar-` Vranged to, beat "therewith forlprod'ucinga ,o in the generated frequency will produce a corresponding change in the generator output to preserve the desired frequency.

4. A constant frequency generating system, comprising a main oscillator and an auX- iliary oscillator arranged to beat therewith for producing a beat frequency within the audible range, a circuit tuned to said beat frequency, rectifyin g means associated with the tuned circuit for producing a direct current proportional to the beat frequency, said beat frequency" varying inversely with Variations in the main oscillator frequency, and an ironcored indictance inserted in the frequency determining circuit of the main oscillator ada-pted to be saturated to a greater or less degree by the rectified direct current to alter the inductance and to thus compensate for any change in the main oscillator frequency.

5. A constant frequency generating system, comprising an oscillation generator subject to slight variations in frequency, a constant frequency heterodyne arranged to beat therewith for producing a beat frequency, a first detector having its input circuit tuned to said beat frequency, a second detector associated with the output of said first detector and having its input circuit tuned to a frequency differing from the beat frequency, and frequency compensating means included in 4Q the frequency controlling circuit of the generator controlled by the rectified current in the output circuit of the second detector for maintaining the generated frequency substantially constant. Y

6. A constant frequency generating sys tem, comprising an oscillation generator sub ,ject to slight variations in frequency, a conj'stant frequency heterodyne arrangedyto beat i' therewith for producing a beat frequency Se within the audible range, a. first detector having its input circuit tuned to said beat frequency, aV second detector having its input circuit tunedv to a frequency higher than the beat frequency and coupled to the output of the first detector, and frequency compensating means connected in the generator output and controlled by rectified current in the output circuit of the second detector for maintaining the generated frequency sub# Gc stantially constant, the magnitude of the controlling rectified current depending upon the difference between the beat Afrequency and the frequency to which the input circuit of the second detector is tuned.

7. The. lmethod of maintaining thefrequency of a high frequency generator substantially constant, which consists in hetero- .dyning the generator output to produce a beat frequency which varies with accidental variations of the desired generated frequency, detecting said unstable beat frequency, then causing the resulting detected current to affect a compensating change in the electrical characteristics of the generator output to preserve the desired generated frequency.

8. The method of maintaining the frequency of a vacuum tube generator substantially constant, which consists in suitably heterodyning the generator output to produce a. beat frequencywithin the audible range, said beat frequency varying inversely with accidental variations of the desired generated frequency, detecting said varying beat frequency, then causing the rectified currents due to changes in beatffrequency to affect a compensating change in the generator output by altering the electrical characteristics thereof to preserve the desired generated frequency.

HENRI CHIREIX. 

